Worm gearing



Feb. 16, 1954 Filed sept. 5, 1952 P. H. sTElNER 2,669,128

WORM GEARING 2 Sheets-Sheet l ToR.

. ,hf/Aff@ Feb. 16, 1954 P, H, sTElNER 2,669,128

WORM GEARING Filed Sept. 5, 1952 2 Sheets-Sheet 2 INVENToR. "fb/fa/Jrf/A/e BYMM'W "Patented Teb. 16, 1954 2,669,1285 womeem er .PhllipilI-ixsteinergcsan nautisch, .scaling assighoi-fotzf:one-thirditus-Edward Bs Gregg, San 'Franirf cieca-calm ApplicationSeptember 5, 1952, seria1 No. 308,067

zlams; (Cl. 'T4-:H4581` tionitofagiven .size of" Worin and gear.

This application is a continuation-in'-part*ofi myfcopendingapplicationsS'erial'.No.. 738,542, led

Aprii; 1:1,194'zev entitled vvzsrm-y Gea-rma no'wf abandoned;

Irnwormggearingf-:the capacityofthefworm 'and thai-matinggearvtovftransmitfpower--depends-upon theszsize oiithe worm .andzthegearing. Anyf de sired.; camteity;` may'v be* achieved simply* by?lconstructing the worm andA the ngearof suilicie'nt size. It?` obviouslyvdesirablerl todesign the Worm tlireadand gear teeth-:torprovidefhighcapacity` Witlr;azi-'.vvormu.antifa@` gear. ofkrelatvel-y vsmall size:This; however,`V is.. limited by` the mechanical strength ioffthe Wormythread'fandgea-r teeth and' byffthe: efllciencyof Athe 'thread-fand?teeth in ltransmtting zpovver from one v'to the other.

The design off' worm, gearing'` heretofore-g; has been inadequate inthat, for heavy load transe-- Itis another object of the invention toprovide* an improved'f worm:l threadi and" matingj gear teeth.:`

Yetianother/object ofthe invention isto pro-s viderasworm 1 thread andgea/rt teeth :ofV :a I' designy whicr'risxmore efcientfforftransmissionofpower; Still a-notherf7 object of the' invention is" to pro vide aworm thread and gear-teeth having greater bei.apparentv from theYensuing; description and f Certain ferrnsffoff the inventionare-illustnated'l Fiigure flifis'f'aviewpartly infrontYelevationandpartly in-flngitudinal'; vertical section; off'on'eform-ot'fwormgearingfconstructed in'y accordanoer` with'l the presentinventions Figure 2 lzisva similar view-fofanother-*form-of` werlrn-.-gearing constructed* accordance Withi Figure 4 is Eaffragxnentary,iltransverse staggered" the manner in which the gearing of the presentinvention entraps and holds lubricant inl con trastwith conventionalgearing.

Figure 6I is a vertical, sectional View showing; the worm gearing ofthepresent invention-en-v closed in a lubricant housing. A

Referring now to the drawings'and-morelpare' ticularlyto' Figure l;one'formof Worm gearingthere` illustrated and is' generally designated*as IU.' The gearing Iii comprisesv a worm It and a mating gear I2.Either of these may beth'e" driving Amember and the otherthe driveninembeix The Worm II has a shaft I3 which is jour-fv naled in bearingsI4; and athread which is genserallyv designated `asA I5, the individualturns thereofbeing designated as I5a, |51), I5`c and I5d. ThevWc'irmthreadl I5 is `of'the hour glass 4type "wherein the profile-of theWorm describes"a'-fig ureresembling an hour glass-as itrotates; 'suchVfigure being shovvn'at' I6. This type of Worm is preferred: Where lextraheavy power requirements mustibe met.

Thegear I z'isshown'as being keyed to 'a shaft" II-h'aving its'centerorvaxis'at I8. The pitch'A circle of thegear is shown at I9; andthe gearis-'formed*withteeth 2i?.` The teeth Zware "designed ttor-fuir meshingrelationwith rthe Vwennl thread i5. Thepitch circle lhasthe saine"radius as the profile of 'the Worin.

There is valso `shown in Figure' 1 an. upper 'set l ofreferencecircles25a, b, c,- etc., and a lower set. ofreferencecircles 26a; b, c, etc.,al1 ofthe same radius.v There isalso shown a vertical reference. line21'Which passes through the center I8` of" the `gear I2` and whichb'isectsA the worm thread I5; The said reference circles and thesaidreferencelinedc not; 'of course, form parts ofthe structureillustrated but are used for reference purposes toA show the manner inwhich theff'aces A ofthegearteeth and Worm 'thread are developed invaccordance with the present invention. Referring to the centrallylocated 'reference circle 25d., it will be seen that its .center 23 islocated" atthe'intersectionof the vertical referencel'ine. A

2Tan'd th Ditch circle I9. It Will'lsb be .Seen thati'th'e faces 29' ofthe Wormthread I5. which. face, the point 28 'and Which-.are located onthe` turns I5b'and ld'on'opposite Vsides offthe ypoint. Y

28; eoincid'ewith therefere'nce circle 2511i. e., the faces. 29 aredeveloped as arcs ofcirclesof radius r, that being. the radius of.thecircle25d;V TheI faces 29A of. theother turns. of the wormw z"th'rea'dj' are similarlydeveloped, as is indicated 'designed inaccordance with thet invention'is'-.

by the upper set of circles 25a, b, etc., and the lower set of circles26a, b, etc.

It will also be apparent that the faces 30 of the gear teeth aresimilarly developed, i. e., as arcs of circles of radius 1. Thus,referring to the two gear teeth on opposite sides of the reference line21, it Will be seen that their faces 3c which face the line 21 coincidewith the circle 25d. All of the gear teeth 20 lare similarly developed.

In this connection it is desired to point out that the referencecircles, or the radius of the faces of the gear teeth and worin thread,may be large or small. However, for large speed ratios of worm to gear Iprefer smaller reference circles (i. e., a smaller radius) and forsmaller speed ratios of Worin to gear I prefer larger reference circles(i. e., a larger radius) As stated, the hour glass type of Worm threadillustrated in Figure l is adapted to extra heavy load requirements. Analternative type of gearing is shown in Figure 2 which embodies theprinciples of the present invention and which may be used where powerrequirements are not as great. Referring to Figure 2 the worm gearing isgenerally designated as 110 and it comprises a Worm 4| having a threadi2 and a shaft d3 which is journaled in bearings mi. The helical thread42 consists, of course, of individual turns Ma, b, etc.

The profile of the Worm el describes an imaginary cylinder 46 as itrotates.

The Worm 4l meshes with a gear il having its center at 48, having apitch circle il@ and having teeth 5U. The appropriate reference circlesare shown at Ela, b, etc., 52a, b, and b, etc. The circles 51e and 32ecoincide. Also shown is a vertical reference line 511 which passesthrough the center 48 of the gear and which transects the worm thread.Circles da, b, etc., 52a, b, etc. and 53a, b, etc. are of the sameradius. Referring to the central circle iiic and to the turns 4219 and`42d of the worm thread, the faces 55 thereof which face reference line54, coincide with the circle 5Ic. The faces of all the turns of the wormthread d2 are similarly developed, i. e., as arcs of circles of thesaine radius. The teeth 5l! of the gear d'1 are similarly developed, aswill be apparent from an inspection of Figure 2.

Yet another embodiment of the invention is illustrated in Figure 3wherein the gearing is generally designated as iid and comprises a worm6I having a shaft 62 journaled in bearings 63. The thread 64 of the wormis in full meshing relation with the teeth 65 of a gear ii having itscenter at 6l and its pitch circle at 68. In this instance, attention isdirected to two reference circles $91) and 69e whose centers 'Fi areequally spaced from a vertical reference line l5. The reference circles69a, b, c and d and the other reference circles bear the same relationto the worm thread and the gear teeth shown in Figure 3 that the circles5m, etc.v bear to the worm thread and gear teeth shown in Figure 2. Thatis, in the embodiment shown in Figure 3 the worm thread and the gearteeth are developed as arcs of circles of the same radius.

It will be apparent that, in the worin gearing #il of Figure 2, thepronle of the worin is tangent to the pitch circle of the gear Whereasin the embodiment shown in Figure 3. the profile of the 'worm intersectsthe pitch circle of the gear. The embodiment shown in Figure 3 ispreferred for medium duty use, the embodiment of Figure 2 for lighterduty and the embodiment of Figure l for heavier duty. As indicated, thecenter turnof the Worm thread 6I in Figure 1 is recessed to coincidewith the pitch circle 68, which is duplicated at 68a.

Referring now to Figure 5, conventional types of gearing are shown at A,B and C. It will be apparent that a lrn of lubricant, indicated at 1B,will be subjected to forces tending to squeeze it out from between theworm thread and gear teeth, and that the meshing relation of the threadand teeth are not such as to maintain a uniform nlm of lubricant. In thegearing illustrated in Figure 5D, which is that of the presentinvention, such tendency is much less likely to occur. A uniform film oflubricant is entrapped :between the gear teeth and worm thread and isnot squeezed out. This is made possible by the full meshing relation ofthe gear teeth and worm thread and by the uniform sliding concentriccontact between the gear teeth and worm thread.

Referring to Figure 6, one means of lubricating the gearing of thepresent invention is there illustrated. This means comprises a housing'H for gearing I!! comprising a Worm il and a gear I2. A body oflubricant is shown at i8 in which the worm and the lower portion of thegear are submerged.

In Figures l, 2 and 3 the centers of the reference circles for the wormthread have, as their locus, the profile of the worm thread and thecenters of the reference circles for the gear teeth have, as their'locus, the pitch circle of the gear.

This is the preferred embodiment of the invenl tion, but some departureof these centers from the indicated loci is permissible.

It will, therefore, be apparent that a novel type of gea ng has beenprovided which is capable ofv I claim: l.. A worm gearing comprising anintermeshing' worin and gear, said worm having a helical, concave threadand said gear having teeth with conf a gear having consecutive teethwith convex working faces in full meshing relation with the workingfaces of the worm thread and for the width of the gear teeth, saidWorking faces being developed as arcs of circles of the same radius, thecenters of the arcs of the gear teeth having as their approximate locusthe points of intersection of the pitch line of the gear and radii ofthe gear bisecting the cavities between gear teeth, each said gear tootharc having as its center an adjacent point of intersection.

4. A worm gearing of the hour glass type comprising a worm having ahelical hour glass thread with concave working faces and a gear meshingwith said worm, said Worm thread having a height in midsection to`coincide with the pitch line of the gear, said gear having consecutiveteeth with convex working faces in full meshing relation with theworking faces of the worm thread and for the full width of the gearteeth, said Working faces being developed as arcs of circles of the sameradius and the centers of the arcs of the gear teeth having as theirapproximate locus the points of intersection of the pitch line of thegear and radii of the gear bisecting the cavities between gear teeth,each said gear tooth arc having as its center an adjacent point ofintersection.

5. A worm gearing of the hour glass type, comprising a gear havingconsecutive teeth with convex Working faces forming the arc of a truecircle having its center located on the pitch line of said teeth at thecenter of the space between adjacent teeth respectively; and a wormhaving a helical thread with an arcuate perimeter concentric with thepitch line of said gear teeth, said Worm thread having concave lateralwork- 6 ing faces lconcentric and meshing with the said convex faces ofsaid gear teeth.

6. A worm gearing of the hour glass type, coinprising a gear havingconsecutive teeth separated by an intermediate space between adjacentteeth, with convex Working faces cach forming the arc of a true circlehaving its center located substantially on the pitch line of said teethat the center of said space between adjacent teeth respectively; and aWorm having a helical thread with an arcuate perimeter concentric withthe pitch line of said gear teeth, said Worm thread having concavelateral Working faces each forming the arc of a true circle and incontact with said convex Working faces of said teeth with which the Wormis meshed.

PHILIP I-I. S'I'EINER.

No references cited.

